Pulverisers are commonly used for crushing large coal or other raw material into small particles. An airstream entering the pulveriser sweeps the particles into a classifier which separates coarse particles from the airstream for regrinding and allows the finer particles to exit the classifier and to be used in a process or burned in a furnace (in the case of coal). Prior art classifiers in some cases are not as effective in returning the coarse particles or are less efficient owing to increased flow resistance caused by turbulence in certain areas within the classifier. Increased turbulence is undesirable as the classifier parts are subjected to increased wear. These inefficiencies limit the capacity of the pulveriser and negatively affect the output of boilers fed by the pulveriser (in the case of coal). Latest boiler requirements for NOx reduction require a finer product than previous type classifiers were designed for. The Inventors desire an improved static classifier which can provide the fineness required in these boilers for low NOx design burners whilst maintaining throughput of these mills.
The Inventors desire a classifier which addresses the above drawbacks.